Listen to Robert Emmerich introduce The Big Apple, a hit song from 1937. Music written by Bob and performed by Tommy Dorsey's Clambake Seven with Bob on piano. Lyrics written by Buddy Bernier and sung by Edythe Wright. Audio provided by Dorothy Emmerich.

In the second-half of the 1800s, students (especially in rural communities) brought an apple to the teacher. The origin of this practice can’t be pinned down to a specific date, but “an apple for the teacher” was well-known by the 1880s and 1890s.

To “polish an apple” originally meant to wash them for sale, but the term “apple-polisher” (also written “apple polisher") meant someone who curries favor with a superior, such as a student who brings an apple for a teacher to help get better grades. “Apple-polisher” became popular college slang in the 1920s.

The 1939 song “An Apple for the Teacher” was recorded by Bing Crosby for the film The Star Maker. Students seldom bring apples for teachers today, for fear of being called “apple-polishers.”

(Historical Dictionary of American Slang)
apple-polisher n [see polish apples S.V. APPLE]
a person who attempts to curry favor with a superior, as a pupil with a teacher; flatterer.
1927 in American Speech 128: Apple-polisher. One who hoses a prof, that is, tries towheedle him out of a good grade.
1964 B. Kaufman Down Staircase 68: Harry Kagan is a politician and apple-polisher.
1966 Elli 243: The apple polishers are startin’ to get in the act.
1968 Brunvand 333: Ask a college class what word they use to denote a fellow student who curries favor with the teacher...Of students over 45, men and women give “appple-polisher” almost without exception.

(Oxford English Dictionary)
apple-polisher n. N. Amer. colloq. a person who attempts to curry favour with a superior; a toady, a flatterer.
1918 N.Y. Times 30 Nov. 10/6 A flash of common sense..might have saved us from being obliged to..contemplate the ideal world as being made up of highly competent *apple polishers and pencil sharpeners.
1929 Oakland (Calif.) Tribune 4 Feb. 1/7 It is a mistaken notion that a co-ed is just an apple-polisher, concerned with nothing but..the good grades she can squeeze out of a prof.
1947 E. A. MCCOURT Music at Close 116 The apple-polishers in the front row laughed with forced heartiness.
1989 D. H. HACKWORTH & J. SHERMAN About Face 400 To me, he was an apple-polisher and an asskisser.
2000 Sun-Herald (Sydney) 18 June 2/3 Surrounded by apple polishers and brown nosers at your office? You’re not the only one. The art of sucking up to the boss is rapidly on the increase.

apple-polishing n. N. Amer. colloq. currying favour, toadying; an instance of this.
1926 Los Angeles Times 21 Feb. II. 4/6 Conversation with pupils, in local academic slang, is known as ‘*apple polishing’.
1929 Oakland (Calif.) Tribune 5 Oct. 24/2 An insincere student, by continually talking with professors about courses may become interested and proficient in his studies. The apple-polishing game, which starts out as one on the instructor, may hit back.
1983 Med. Lab. Observer (Nexis) Jan., Volunteering assistance with these chores isn’t apple-polishing; it just shows a willingness to contribute to the team.
2006 New Yorker (Nexis) 22 May 81 A little apple-polishing is understandable for a reporter whose day job depends upon access.

31 December 1887, Newport (RI) Mercury, pg. 8, col. 2:
Here were found two small trees, a “horn of plenty” five feet long, and several tables all heavily laden with more than 800 gifts, ranging in value from a fine gold watch down to a six-cent handkerchief, besides an orange for each member of the school and a big apple for each teacher.

27 June 1896, The Broad Ax (Salt Lake City, UT), pg. 2, col. 1:
Spain professes the utmost for the United States. This rather reminds one of the whipped schoolboy who comes to school the next day with an apple for the teacher.

12 October 1897, Duluth (MN) News-Tribune, pg. 4:
SEATTLE ENGLISH.
From the Pioneer Press.
The Seattle Post-Intelligencer, philosophizing on the text, “A Red Apple for the Teacher,” speaks of the boy who presents a red apple to the teacher every morning as a “truculent” boy; of a distribution of apples among one’s schoolmates, in order to gain favor, as an act of “truculence;” and of a subservient newspaper as a “truculent” sheet. Ifthere are no dictionaries in Seattle, the editor of the Post-Intelligencer should take a big red apple to the nearest schoolmarm and ask her the meaning of the word “truculent.”

18 October 1926, Waterloo (Iowa) Evening Courier, pg. 6, col. 4:
“APPLE POLISHERS.”
Ottumwa Courier; College students have coined a new term, An “apple polisher,” according to the Columbia Missourian, is one “who goes up after class and tries to get in good with the teacher by expressing his interest in the work and telling how much he enjoyed every bit of it.”

Google News Archive
28 November 1950, Pittsburgh (PA) Post-Gazette, pg. 12, col. 1:
An Apple for Teacher
Pittsburgh’s public school teachers aren’t satisfied with the $200 a year pay increase voted them by the Board of Education. They think they ought to have more.

The only consolation we can offer them is that, in relation to their fellow workers in the educational vineyard, they aren’t doing too badly.